Stereoretentive Palladium‐Catalyzed Arylation, Alkenylation, and Alkynylation of 1‐Thiosugars and Thiols Using Aminobiphenyl Palladacycle Precatalyst at Room Temperature

Abstract

A general and efficient protocol for the palladium-catalyzed functionalization of mono- and polyglycosyl thiols by using the palladacycle precatalyst G3-XantPhos was developed. The C-S bond-forming reaction was achieved rapidly at room temperature with various functionalized (hetero)aryl-, alkenyl-, and alkynyl halides. The functional group tolerance on the electrophilic partner is typically high and anomer selectivities of thioglycosides are high in all cases studied. New sulfur nucleophiles such as thiophenols, alkythiols, and thioaminoacids (cysteine) were also successfully coupled to lead to the most general and practical method yet reported for the functionalization of thiols.

Immobilization of UDP‐Galactose on an Amphiphilic Resin

“…Glucose, 4 , was acetylated in a quantitative yield with acetic anhydride, catalysed by 4‐ N , N ‐dimethylaminopyridine (DMAP) . Sugar 5 was produced by the glycosylation reaction of p ‐toluenethiol with the C1‐hydroxyl in a good yield of 78 % over two steps , . The remaining acetyl groups were removed and an acetal introduced to C4 and C6 formed sugar 6 in a good yield of 66 % over two steps .…”

“…Sugar 5 was produced by the glycosylation reaction of p ‐toluenethiol with the C1‐hydroxyl in a good yield of 78 % over two steps , . The remaining acetyl groups were removed and an acetal introduced to C4 and C6 formed sugar 6 in a good yield of 66 % over two steps . Benzylation of C2 and C3 followed by the removal of the acetal group under acidic conditions gave sugar 7 in an excellent yield of 94 % over two steps.…”

“…BF 3 · OEt 2 (771 µL, 6.25 mmol) was added at 0 °C and the reaction mixture warmed to room temperature before being stirred for 2 d. The reaction mixture was washed with NaHCO 3 (20 mL) and the aqueous phase extracted with CH 2 Cl 2 (3 × 10 mL) and the combined organic phases were dried and concentrated in vacuo. Purification by flash chromatography (8:2, hexane/ethyl acetate) gave the product as a yellow solid (445 mg, 78 %) , . The sugar (135 mg, 0.30 mmol) and NaOMe (10 mg, 0.18 mmol) were stirred in MeOH (3 mL) for 1.5 h. The reaction mixture was quenched with Dowex, filtered and concentrated in vacuo to yield the product as a yellow solid (80 mg, 94 %) .…”

“…Purification by flash chromatography (8:2, hexane/ethyl acetate) gave the product as a yellow solid (445 mg, 78 %) , . The sugar (135 mg, 0.30 mmol) and NaOMe (10 mg, 0.18 mmol) were stirred in MeOH (3 mL) for 1.5 h. The reaction mixture was quenched with Dowex, filtered and concentrated in vacuo to yield the product as a yellow solid (80 mg, 94 %) . The sugar (492 mg, 1.71 mmol), PhCH(OMe) 2 (520 mL, 3.44 mmol) and camphorsulfonic acid (cat.…”

Efficient Buchwald–Hartwig–Migita Cross‐Coupling for DNA Thioglycoconjugation

“…In our efforts to functionalize sugars under transition‐metal catalysis, our group recently reported an efficient protocol for the palladium‐catalyzed coupling of aryl and alkenyl halides with various α‐ and β‐glycosyl thiols . The C−S bond‐forming reaction was rapidly achieved (5 min) at room temperature by using G 3 ‐XantPhos palladacycle pre‐catalyst (1 mol %), in the presence of Et 3 N (1.0 equiv) in THF.…”